Marina Supplies

[sparks1234]

Need some opinions here.
We have looked at installing some supplies for boats on what is basically a marina, the distances though when added up become quite large. Maximum length is about 300 mtrs, I don't have a problem working cable sizes out, voltage drop etc but I would value your opinion on whether it would be best to make each socket outlet a mini TT system, basically running a a cable the length of the marina, taking a feed off at each appropriate point via a switch and RCBO to control the socket outlet and push a stake in, obviously keeping the earths isolated.

 

[boatnik1]

You might be as well to check the marina insurers as some of these companies will have their own specs that you have to work to. Some of them limit each outlet load to only 5a and always through a waterproof box with isolator and RCBO at each outlet..

 

[sparks1234]

Ok, sent off e-mail to insurers, all the sockets will be RCD protected individually, its just whether we creatye seperate TT systems

 

[Spudnik]

Have a look in the regs.

There is a specific section for marinas, so it may give you some info there about earthing.

 

[sparks1234]

Nothing in there, I am really considering the distances and getting disconnection times, I know when I did a pool house supply a couple of years ago the inspector from Elecsa said to isolate the earth and make it a TT system

 

[Spudnik]

Nothing in there, I am really considering the distances and getting disconnection times, I know when I did a pool house supply a couple of years ago the inspector from Elecsa said to isolate the earth and make it a TT system

Ah fair enough.

If thats the case then maybe that could be the best way, providing there is suitable ground.

 

[shetland]

What are the current earthing arrangements for the supply? TNC-S is prohibited for marinas under the ESQCR regs so unless it is TNS you would need to TT it anyway. Not sure I see the need to stick a rod in at each socket outlet . You would be using an RCD at the source to meet the disconection times. There is a Wiring Matters magazine with a marinas article in it which you can find on the IET website. May be of interest.

 

[sparks1234]

Have been in touch with ECA and as you said tncs is not allowed, they suggested that 100mA time delay at distribution board and then individual rcd at each socket, main supply is tns so thats good

 

[shetland]

Yes, 100mA time delay with a 30mA for each individual socket is the way to go. Voltage drop over 300m may be a problem. Just out of curiosity what load are you designing for?

 

[sparks1234]

They are looking to have up to 7 outlets and they reckon a max of 10 amps (limited by RCBO ) and a maximum of 50% at any one time, but, at about 90 mtrs from the original distribution board they want facility for a 30 amp welder, so, what I was thinking was a 60 amp supply to a dis board local to the welder, then away from there with probably a cable controlled by a 40 amp circuit breaker, then at each point the 10 amp RCBO.

 

[desertbootz]

Be warned, modern Invertors, MIG/MAG or TIG welders are likely to have robust EMC Filters that could 'leak' quite a bit to Earth. Don't be too surprised if it's greater tham 30mA. Not sure what that means for your design as I'm presuming the outlet for welder needs RCD under the regs?